core: minor evm polishes and optimizations

core/vm/intpool.go

@@ -32,24 +32,36 @@ func newIntPool() *intPool {
 	return &intPool{pool: newstack()}
 }
 
+// get retrieves a big int from the pool, allocating one if the pool is empty.
+// Note, the returned int's value is arbitrary and will not be zeroed!
 func (p *intPool) get() *big.Int {
 	if p.pool.len() > 0 {
 		return p.pool.pop()
 	}
 	return new(big.Int)
 }
+
+// getZero retrieves a big int from the pool, setting it to zero or allocating
+// a new one if the pool is empty.
+func (p *intPool) getZero() *big.Int {
+	if p.pool.len() > 0 {
+		return p.pool.pop().SetUint64(0)
+	}
+	return new(big.Int)
+}
+
+// put returns an allocated big int to the pool to be later reused by get calls.
+// Note, the values as saved as is; neither put nor get zeroes the ints out!
 func (p *intPool) put(is ...*big.Int) {
 	if len(p.pool.data) > poolLimit {
 		return
 	}
-
 	for _, i := range is {
 		// verifyPool is a build flag. Pool verification makes sure the integrity
 		// of the integer pool by comparing values to a default value.
 		if verifyPool {
 			i.Set(checkVal)
 		}
-
 		p.pool.push(i)
 	}
 }